1. Field of the Invention
The present invention relates to a compact telephoto zoom lens having a zooming ratio of 3 or so.
2. Description of the Prior Art
In a four-group zoom lens which has an afocal variator system consisting of focusing group, variator group and compensator group, and a relay system, it is generally necessary to make the entire system very compact in consideration of its commodity worth if its zooming ratio is 3 or so. If a negative refracting power of a second group as variator group is made stronger for attaining the compactness, it becomes such a factor that the Petzval sum is greatly negative and further spherical aberration, astigmatism, coma and chromatic aberration due to zooming are inclined to be greatly varied. And, if a refracting power of a first group as focusing group is made stronger for attaining the compactness, fluctuation of spherical aberration and astigmatism become large at the time of short distance focusing at the long focus side so that an imaging performance is inclined to be greatly deteriorated. Further, if a fourth group as relay system is made a structure of telephoto type for attaining the compactness of the entire lens system, large zonal spherical aberration and astigmatic difference create and the production of chromatic aberration is remarkable so that it was difficult to maintain excellent imaging performance over the whole of zooming range.